The present invention relates an energy storage device and a method for operating an electric energy storage device.
Electric energy stores are used for the operation of electrical systems, such as, for example, in hybrid or electric vehicles. In addition, electric energy stores are also used in different stationary systems, for example to ensure an uninterrupted current supply in the event of a breakdown or an interruption of an energy supply network. In this regard, batteries which are subdivided into individual modules are particularly known as energy stores. These single modules can be individually selected. In this way, a series connection of selected modules of the battery can be facilitated, wherein the battery terminal voltage can be adjusted by the number of the selected and serially connected modules. Such systems are, for example, known from the German patent application DE 10 2010 027 861 A1. In accordance with a battery voltage to be provided, only a portion of the modules present in the battery is generally required for the application. The remaining modules are then deactivated.
The sum of the voltages of the active, serially connected modules therefore delivers the total battery voltage. A charging or, respectively, discharging current of the battery thus flows only through the active modules.
Because the modules of the battery are stressed to varying degrees and are discharged or, respectively, charged during such an operation using a selective and changing configuration of individual modules within the battery, the individual characteristics, such as state of charge or ageing, of the individual battery modules vary.
There is therefore a need for an energy storage device and a method for operating an energy storage device using an efficient selection of individual energy modules. There is furthermore a need to select the individual energy storage modules in such a way that said individual storage modules can be used as efficiently as possible during the entire service life thereof.